In one known method for making such a heat exchanger, especially where the latter is intended for use as a condenser in an air conditioning installation for a motor vehicle, the ends of the fluid flow tubes are introduced into respective ones of the apertures in the tubular wall of the header. The tubes are then displaced parallel to the direction of their length, until their ends come into abutment against the internal surface of the fluid header.
Since the profile of this internal surface is generally circular, the ends of the tubes make contact with the wall at the level of the centre of its circular profile if their width in the radial direction is equal to its diameter. If the width of each tube is smaller than the diameter of the internal surface of the tubular header, the ends of the tubes make contact with the latter beyond its centre; and the smaller the ratio of tube width to wall diameter, the further away is the point of contact between the end of the tube and the interior of the wall. The space which is available in the fluid header facing towards the ends of the tubes can thus become too small for satisfactory fluid flow to occur between the tubes and the header. In addition, this space may vary from one tube to another due to manufacturing tolerances.